It is well known that the crystalline polymorph form of a particular drug is often an important determinant of the drug's ease of preparation, stability, solubility, storage stability, ease of formulation and in vivo pharmacology. Polymorphic forms occur where the same composition of matter crystallizes in a different lattice arrangement resulting in different thermodynamic properties and stabilities specific to the particular polymorph form. In cases where two or more polymorph substances can be produced, it is desirable to have a method to prepare each of the polymorphs in pure form. In deciding which polymorph is preferable, the numerous properties of the polymorphs must be compared and the preferred polymorph chosen based on the many physical property variables. It is entirely possible for example that one polymorph form can be preferable in some circumstances where certain aspects such as ease of preparation, stability, etc. are deemed to be especially important. In other situations, for example, a different polymorph may be preferred for greater solubility and/or superior pharmacokinetics.
Because improved drug formulations, showing, for example, better bioavailability or better stability are consistently sought, there is an ongoing need for new or purer polymorphic forms of existing drug molecules. The various crystalline polymorphs of Compounds 1 or 1a described herein help meet these and other needs.